The subject invention generally relates to ink jet printing, and more particularly to thin film ink jet printheads for ink jet cartridges and methods for manufacturing such printheads.
The art of ink jet printing is relatively well developed. Commercial products such as computer printers, graphics plotters, and facsimile machines have been implemented with ink jet technology for producing printed media. The contributions of Hewlett-Packard Company to ink jet technology are described, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985); Vol. 39, No. 5 (October 1988); Vol. 43, No. 4 (August 1992); Vol. 43, No. 6 (December 1992); and Vol. 45, No. 1 (February 1994); all incorporated herein by reference.
Generally, an ink jet image is formed pursuant to precise placement on a print medium of ink drops emitted by an ink drop generating device known as an ink jet printhead. Typically, an ink jet printhead is supported on a movable carriage that traverses over the surface of the print medium and is controlled to eject drops of ink at appropriate times pursuant to command of a microcomputer or other controller, wherein the timing of the application of the ink drops is intended to correspond to a pattern of pixels of the image being printed.
A typical type of ink jet printhead includes an array of precisely formed nozzles in an orifice plate that is attached to an ink barrier layer, which in turn is attached to a thin film substructure that implements ink firing heater resistors and apparatus for enabling the resistors. The ink barrier layer defines ink channels including ink chambers disposed over associated ink firing resistors, and the nozzles in the orifice plate are aligned with associated ink chambers. Ink drop generator regions are formed by the ink chambers and portions of the thin film substructure and the orifice plate that are adjacent to the ink chambers.
One weakness of inkjet technology is that nozzles or ink injectors can sometimes fail, leaving some areas of the image unpainted, thus eliminating information on the image, which can result in aesthetical problems or uncompleted information on the image.
Ink-jet printheads are typically serviced to minimize these problems. Often, however, reliability problems of new ink injectors appear or become known when the product is already on the market. This can be a problem, as the servicing and printer design has been fine tuned only for known problems.
In the past when a printhead reliability problem appeared, a typical methodology for addressing a problem on the printhead included understanding and fixing the problem on the printhead, and implementing the printhead fix in subsequently manufactured printheads. Users would replace the existing printheads with the reliability problem with the new printheads after failure or replacement in the normal course of usage.
Sometimes, a code change on the machine can help solve reliability problems. In this case, the code change is implemented in the code of newly manufactured machines, and the revised code can be posted on the manufacturer's internet web site for downloading by affected users.
For a problem on a printer mechanism or printer firmware, several techniques have been employed. If the problem solution involves changes in mechanical parts, the solution is implemented on new production machines. For some large problems, the parts on existing machines can be replaced with new parts.
If the problem can be fixed with a printer's code change, the code change is implemented on newly fabricated machines and users can be advised to change the code on the existing printers.
Sometimes a process can help fix the problem. In this case, the fixing procedure can be communicated to the users and some tools sent to the users. For example, a printing system may have a paper pick problem, and a tool kit having an emery board for roughing up a pick roller and an instruction sheet can be furnished to the user.